Listen to Beethoven's 5th. He's starting with this BababaBaaaaa and it's more or less all he uses to build a long track. Actually you don't need much to stell a story. When you have a motive you can do creative things with it. Repeat it, repeat it on different steps, transpose it, stretch it, shrink it, turn it upside down, reverse it, give it to different ranges, use it as bass figure, play it on different modes, make it big, reduce it, use ornaments, use fragments, make it a question or an answer, use it as one part of a dialogue, make it a part of a larger structure, harmonize it, reharmonize it, make it consonant, make it dissonant... and at that point you didn't even start to orchestrate.
It's a bit like jokes. Many jokes belong into categories. Lonely man on a small one palm island jokes. Boss & employee jokes. Cheating dad and smart children jokes. Woman at the doctor jokes. Car driver and police man jokes. Endless list of well known cliches. But the fun is to get something unexpected out of those well known situations. Use your ideas as a starting point.
Beside that it isn't wrong to write short tracks. But if you want to write longer tracks it's good to look how others did it. It's not a miracle.